Figure 7.

Pathway of (3S-3′S)-astaxanthin biosynthesis in H. pluvialis. Major carbon flux during the red stage of H. pluvialis cultivation is indicated with thick arrows, minor products are indicated with thin arrows. Major intermediates of biosynthesis are indicated in large fonts, minor intermediates in small fonts. Enzyme abbreviations are as follows: IPI, Isopentenyl pyrophosphate isomerase; HDR, 4-hydroxy-3-methylbut-2-enyl diphosphate reductase; GGPS, geranylgeranyl pyrophosphate synthase; PSY, phytoenesysthase; PDS, phytoenedesaturase; ZDS, ζ-carotene desaturase; LCY-b, lycopene β-cyclase; LCY-e, lycopene ε-cyclase; BKT, β-carotene ketolase; CrtR-b, β-carotene 3,3′-hydroxylase; Intermediates: Phytofluene, Neurosporene, γ-carotene, β-Cryptoxanthin, Adonixanthin, Echinenone, Adonirubin.